Acid milling of phthalocyanine pigments



United States Patent ACID MILLING OF PHTHALOCYANINE PIGMENTS Robert E. Brouillard, Westfield,-and Thomas D. 'Mutalfis,

North Plainfield, N. J., and Marvin 0. Shrader, Pittsburgh, Pa.

No Drawing. Application April 29, 1953 Serial No. 352,021

11 Claims. c1. 260--314.5)

phthalocyanine pigments comprising milling with shearing forces a mixture comprising a phthalocyanine pigment and a quantity of a strong, normally liquid nonoxidizing acid suflicient to produce with the pigment a doughy kneadable mass, and drowning the resulting magma in water. highly desirable results. It eliminates the disadvantages attributable to the prior methods of acid pasting which require large amounts of acid. The process also greatly shortens the treatment time, produces a presscake with a relatively high solids content, and is applicable to pigments which are unstable to conventional acid pasting.

While the process of said copending application is satisfactory in most instances, the products produced That process enables the attainment of thereby sometimes do not have the transparency 'propera ties required for certain purposes. Such transparency properties are important in several end uses in which the phthalocyanine pigments are employed. In the production of multi-color effects in which other colors are used in conjunction with the phthalocyanine pigment in the production of coating and printing compositions, selfsupporting films, and other solid objects, it is necessary that the phthalocyanine pigment have transparent properties in order to obtain the desired gross effects. Also,

in the production of iridescent effects obtained by mixing 7 I phthalocyanine pigments with aluminum flakes in a ve- It is an object of this invention to provide a process which will have all of the advantages of the process-of said copending application and which will produce phthalocyanine pigments having improved transparency properties. Other objects. and advantages will appear as the description proceeds.

The above objects are attained by the instant invention which is directed to a process comprising milling with forces predominantly shearing in nature, a mixture comprising a phthalocyanine pigment, an acid-stable, water-soluble inorganic salt and a quantity of a strong normally liquid non-oxidizing acid sufficient to produce with the pigment and salt a doughy kneadable mass, and drowning the resulting milled mixture in water. The aqueous mixture is then filtered and washed acid free.

The procedure of this invention is suitable for the conditioning of any phthalocyanine such as metal free particular pigments treated and the like.

' stance.

sulfuric acid and the pigment is copper phthalocyanine, 65

phthalocyanine, metal phthalocyanines, such as copper, nickel, cobalt, zinc and lead phthalocyanines, halogenated metal and metal free phthalocyanines such as copper octachloro phthalocyanine, copper hexadecachloro phthalocyanine, and the like.- The phthalocyanine may also be nuclearly substituted with nitro, amino, thio, oxy, carbonyl, alkoxy, aryl, aryloxy and other groups.

The acid-stable, water-soluble salts employed in the process of this invention are in general alkali metal sulfates and phosphates, as for example, sodium and potassium sulfates, acid sulfates, phosphates, acid phosphates, and the like. The amount of salt required for optimum performance should be at least one-half part by weight per part of pigment. Generally, no more than five parts by weight of salt per partof pigment is-required since larger amounts require higher acid consumption and thus interfere with the basic economic advantages of the instant process.

Operative'strong, non-oxidizing normally liquid acids for the purpose of the instant process are sulfuric, phosphoric, chlorosulfonic, chloroacetic and lower alkylsulfonic acids such as methyl sulfonic, ethyl sulfonic and the like. The greatest economy and best results are obtained with sulfuric acid and the use of this acid is, therefore, preferred.

One of the essential features of this process is the.quan- .tity of acid employed. Such quantity should bethat necessary to produce with the pigment and salt a doughy kneadable mass. The particular quantity of acid which will give this result can be readily determined by experi mentation. Thus, if the quantity is too small, the pigment does not wet out completely. Too great a quantity of acid, on the other hand, does not allow adequate shearing, and leads to lumpy masses in which the acid does not contact all pigment particles in addition to requiring larger quantities of salt. In general, the-quantity of acid will be within the range of about 0.5 to 2' parts by Weight per part of pigment. It is possible to 'vary the pigment-salt-acid ratio after the mass has been mined under shearing in order to improve theease with which the mixture may be discharged from the mill. Observation of the aforestated condition, however, is necessary when the shearing action is originated in order to obtain the desired results.

The concentration of the acid will, of course, depend somewhat upon the particular acid employed and the Generally speaking, however, the concentration will range from about 68 to percent. Simple tests will be sufiicient to indicate the specific concentration within this range which will give optimum results in any particular in- Thus, it may be said that if the acid used is best results are obtained with a concentration of. acid ranging from about 79 to 82 percent; A concentration.

of about 94 to 98 percent sulfuric acid gives best results where the pigment is copper hexadecachloro phthalocyanine. It is therefore to be emphasized that while the results of our invention will be obtained by using a strong liquid non-oxidizing acid having a concentration withinthe range of about 68 to 100 percent, optimum results are obtained by varying the concentration within this range to suit the particular pigment being treated and the like.

The particular apparatus used for effecting the milling of the pigment-salt-acid mass must be one capable of exerting a substantially uniform shearing action throughout the mass. Any apparatus capable of so operating is suitable. We prefer to use a Werner-Pfieiderertype of mill, but Banbury mixers or other mills may be employed which operate by other mechanisms such as by extrusion provided that they operate to exert a uniform shearing force on the composition being milled.

The temperature at which the process is carried out is not critical and may in fact vary. between. the melting point and the boiling point ofthe composition'being milled, .as for example, between aboutQO to 150 C. There is a definite relationship betweenjthe temperature employed and the' acid concentration'required to'give optimum results withfia particular pigment; Higher temperatures generally require lower acid concentrations. For practical reasons we. prefer to operate in the temperature range ofabout 20 to 50 C. since'unjacketcd equipment may thus be employed. The milling time under shear is. also dependent on other factors and may range from as little as about 5 minutes to as much as 5 hours or molfc the hotter periods beingjpreferred whenever possible for obvious reasons.

The following examples, in which parts are by weight unless otherwiseindicated are illustrative of the instant inventionand arenot to be regarded as ,limitative.

i i i l 2 Example I 100 parts of copper hexadecachlorophthalocyanine, 100 parts of 96 percent. sulfuric acidand 200 parts of sodium sulfate were introduced into a Werner-Pfieiderer mill and substituted for sodium sulfate.

Exa'rnple II JQOMpaIts Of, copper. phthalocyanine, 75 parts of. 8 1

vpercent sulfuric acid and 200 parts of sodium sulfate were introduced into a Werner-Pfleiderer mill and milled for 2 hours. The magma was discharged into .1000 parts of water under agitation- Thejslurry which. resulted. was filtered and the cake washed acid-free.

The product obtained had excellent transparency and t r p s ary p perties.

Example III v 100 1:vaits of metal free phthalocyanine, 50 parts of 72 A 1.A process comprising milling with forces predominantly shearing in nature, a mixture in the form of a doughy, kneadable mass comprising a phthalocyanine pigment, from about 0.5 to 5 parts by weight per part of pigment of an acid-stable, water-soluble inorganic salt and from about 0.5 to 2 parts by weight per part of pig ment of a strong, normally liquid, non-reactive acid having a concentration ranging from 68 to 100 percent, and drowning the resulting milled mixture in water.

2. The process of claim 1 in which the acid is sulfuric acid.

3. The process of claim 1 in which the salt is selected from the group consisting of alkali metal sulfates, acid 7 concentration of about 68 to 100 percent.

percent sulfuric acid andl25 parts of sodium sulfate were introduced into a Werner-Pfieiderer mill and milled for onehour. The magma was discharged into 1000 parts 5. The process of claim 1 in which the phthalocyanine is copper phthalocyanine, the salt is sodium sulfate, and the acid is sulfuric acid employed in a concentration of about 68 to percent. 7

6. The process of claim 1 in which the phthalocyanine is metal-free phthalocyanine, the salt is sodium sulfate and the acid is sulfuric acid employed in a concentration of about 68 to 100 percent.

7. The process of claim 1 in which the salt is sodium sulfate.

8. The process of claim 10 in which the salt is sodium sulfate.

9. The process of claim 8 in which the acid is sulfuric acid.

'10. A process comprising milling with forces predominantly shearing in naturea mixture in the form of a doughy, kneadable mass comprising a phthalocyanine pigment, from about 0.5 to 5 parts by weight per part of pigment of an acid-stable water-soluble inorganic salt, and from about 0.5 to 2 parts by weight per part of an acid selected from the group consisting of sulfuric, chloroacetic, phosphoric, chlorosulfonic and lower alkyl sulfonic acids having a concentration ranging from 68 to 100 percent,- and drowning the resulting milled mixture in water.

11. The process of claim 10 in which the salt is selected from the group consisting of alkali metal sulfates, acidsulfates, phosphates and acid phosphates.

References Cited in the file of this patent UNITED STATES PATENTS- Carr Apr. 7, 1942 Detrick et a]. June 2, 1942 Lang June 18, 1946 Barnhart Oct. 2, 1956 vol. III. 

1. A PROCESS COMPRISING MILLING WITH FORCES PREDOMINANTLY SHEARING IN NATURE, A MIXTURE IN THE FORM OF A DOUGHY, KNEADABLE MASS COMPRISING A PHTHALOCYANINE PIGMENT, FROM ABOUT 0.5 TO 5 PARTS BY WEIGHT PER PART OF PIGMENT OF AN ACID-STABLE, WATER-SOLUBLE INORGANIC SALT AND FROM ABOUT 0.5 TO 2 PARTS BY WEIGHT PER PART OF PIGMENT OF A STRONG, NORMALLY LIQUID, NON-REACTIVE AID HAVING A CONCENTRATION RANGING FROM 68 TO 100 PERCENT, AND DROWING THE RESULTING MILLED MIXTURE IN WATER. 